Transport of phospholipid in silicone hydrogel contact lenses

Characterization of the transport and release of phospholipids from a silicone hydrogel contact lens is required to assess the possible use of these lenses for phospholipid delivery to increase patient comfort. Contact lenses of silicone hydrogel composition were loaded with varying amounts of radiolabeled 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) from a solution of n-propanol. These lenses were eluted at 35°C into artificial tear fluid (ATF) or ATF containing varying amounts of DMPC. The amount of DMPC loaded into a lens is a linear function of the time of exposure to the DMPC/propanol solution. The initial rate of elution into ATF appears to be diffusion controlled for at least 10 h and is proportional to the amount of DMPC loaded. The elution rate decreases as the DMPC concentration in the ATF increases. The ease of loading and the controllable release of DMPC from silicone hydrogels presents the possibility of using such lenses to counter eye discomfort caused by inherently low levels of phospholipid in tears.